LSX376 timing / knock sensor tuning

[RivMan]

Hello!

I've recently swapped out my L92 (Aluminum 6.2, 10.5:1, VVT Truck cam) with an LSX376-B8 (LSX Bowtie Iron block 6.2, 9:1, LS3 cam).

My goal for the build was to put together a super reliable, lazy, low compression motor that can run on any fuel I dump into it (Think South American villages where the "Gas Station" is a bunch of sketchy 2-liter bottles on a picnic table on the side of the road.)

I'm running a pretty stock L92 based tune, and have the truck running well.

• MAF tuning
• MAP Tuning
• VVT Disabled
• Torque management dialed down
• Trans parameters tweaked
• LTFT's +/- 1.5 degrees
• Zero KR, towing on 87 Octane (Just completed a 6,000 mile round trip, weighed in at 10,500 lbs with the trailer)

One thing that I haven't touched at all from the stock truck tune is the timing tables and knock detection parameters.

I'm wondering if there are any Knock detection parameters that should be changed when moving from an Aluminum to an Iron block. I don't expect this setup to be into knock with the low compression, but I'm skeptical that there's truly ZERO knock. I've only seen a small blip of 0.1 a couple times, when accelerating hard through a downshift. I want to make sure the system is functioning as intended.

I'm planning to swap my timing tables over to an LS3 based table, instead of the truck table, which looks a bit more aggressive.

Thanks
-Rob

[Cringer]

Hello!

I've recently swapped out my L92 (Aluminum 6.2, 10.5:1, VVT Truck cam) with an LSX376-B8 (LSX Bowtie Iron block 6.2, 9:1, LS3 cam).

My goal for the build was to put together a super reliable, lazy, low compression motor that can run on any fuel I dump into it (Think South American villages where the "Gas Station" is a bunch of sketchy 2-liter bottles on a picnic table on the side of the road.)

I'm running a pretty stock L92 based tune, and have the truck running well.

• MAF tuning
• MAP Tuning
• VVT Disabled
• Torque management dialed down
• Trans parameters tweaked
• LTFT's +/- 1.5 degrees
• Zero KR, towing on 87 Octane (Just completed a 6,000 mile round trip, weighed in at 10,500 lbs with the trailer)

One thing that I haven't touched at all from the stock truck tune is the timing tables and knock detection parameters.

I'm wondering if there are any Knock detection parameters that should be changed when moving from an Aluminum to an Iron block. I don't expect this setup to be into knock with the low compression, but I'm skeptical that there's truly ZERO knock. I've only seen a small blip of 0.1 a couple times, when accelerating hard through a downshift. I want to make sure the system is functioning as intended.

I'm planning to swap my timing tables over to an LS3 based table, instead of the truck table, which looks a bit more aggressive.

Thanks
-Rob

This LS3 knock sensor (PN 12623730) is used on many different vehicles. Scroll down to Vehicle Fitment to see all the models it is used on.

https://www.gmpartsdirect.com/oem-parts/gm-ignition-knock-detonation-sensor-12623730?c=bD0xJm49U2VhcmNoIFJlc3VsdHMmYT1jaGV2cm9 sZXQmbz1zcyZ5PTIwMTQmdD1iYXNlJmU9Ni0ybC12OC1nYXM%3 D

[RivMan]

This LS3 knock sensor (PN 12623730) is used on many different vehicles. Scroll down to Vehicle Fitment to see all the models it is used on.

https://www.gmpartsdirect.com/oem-parts/gm-ignition-knock-detonation-sensor-12623730?c=bD0xJm49U2VhcmNoIFJlc3VsdHMmYT1jaGV2cm9 sZXQmbz1zcyZ5PTIwMTQmdD1iYXNlJmU9Ni0ybC12OC1nYXM%3 D

Thanks, Cringer

I realize the knock sensor is the same between the two engines, however I'm concerned that the "Signature" of knock is different. As I understand it, the sensors "listen" to the vibrations of the block, looking for specific frequencies that are associated with knock. This signature seems to be in the calibration, and seems to be specific to the block material and bore size.

-Rob

[Cringer]

Thanks, Cringer

I realize the knock sensor is the same between the two engines, however I'm concerned that the "Signature" of knock is different. As I understand it, the sensors "listen" to the vibrations of the block, looking for specific frequencies that are associated with knock. This signature seems to be in the calibration, and seems to be specific to the block material and bore size.

-Rob

I don't think there is anything you can realistically do other than compare the knock settings from the other ECM's and copy them over. Any signal processing will be buried deep in the ECM code, and unless you are a wizard you can't move that over. I would not sweat going from an Aluminum to Iron block of the same bore size. I would just use the OEM settings you currently have. If you want, you can lower the values in the [ECM] 12971 - Knock Sensor Threshold Min table to make the ECM more sensitive to output from the knock sensors, which would trigger a knock scenario more easily to pull timing.

You can get Knock Ears to listen for tuning or you can periodically pull spark plugs to look for detonation, or use a bore scope to look for pitting on the piston crowns.

[Alvin]

I wouldn't change the knock sensor settings.

If you concerned the knock sensors aren't working.. run the timing up just to see knock as a test.

Early chip cars were like this.. They would throw a knock sensor fault if during a highway test running up the timing didn't pick up knock.

[verlon]

I'm wondering if there are any Knock detection parameters that should be changed when moving from an Aluminum to an Iron block.

No. I have two VINs for 2007 trucks with LC9 (aluminium) and LY5 (iron) which has completely identical calibrations.
Knock sensor settings majorly depends on the piston top configuration (dish/flat/dome, valve reliefs) which determines its resonant frequency.